Delphi DLL Requires Chilkat v11.0.0+

Validate a Google ID Token

See more OAuth2 Examples

Demonstrates how to verify the signature of a Google id token. Delphi DLL

var
success: Boolean;
http: HCkHttp;
jwkStr: PWideChar;
json: HCkJsonObject;
jsonToken: HCkJsonObject;
sbIdToken: HCkStringBuilder;
sig_b64Url: PWideChar;
headerPlusPayload: PWideChar;
rsa: HCkRsa;
jsonKey: HCkJsonObject;
pubKey: HCkPublicKey;
numKeys: Integer;
i: Integer;
bVerified: Boolean;

begin
success := False;

//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

http := CkHttp_Create();

//  First get the public key we'll be needing..
jwkStr := CkHttp__quickGetStr(http,'https://www.googleapis.com/oauth2/v3/certs');
if (CkHttp_getLastMethodSuccess(http) = False) then
  begin
    Memo1.Lines.Add(CkHttp__lastErrorText(http));
    Exit;
  end;

//  We have the following:

//      {
//        "keys": [
//  	{
//  	  "kid": "e8732db06287515556213b80acbcfd08cfb302a9",
//  	  "n": "4RIrO30287Wsq3gqXCMkUYMVAeI3H8...w2mbMNEBQ",
//  	  "kty": "RSA",
//  	  "e": "AQAB",
//  	  "alg": "RS256",
//  	  "use": "sig"
//  	},
//  	{
//  	  "kid": "8462a71da4f6d611fc0fecf0fc4ba9c37d65e6cd",
//  	  "e": "AQAB",
//  	  "n": "xT_ngLZNmT5GBtJZeTB...Ft4gK0eoFi0d3l8bcw",
//  	  "alg": "RS256",
//  	  "use": "sig",
//  	  "kty": "RSA"
//  	}
//        ]
//      }

json := CkJsonObject_Create();
success := CkJsonObject_Load(json,jwkStr);

//  -------------------------------------------------

//  Load the following..

//   {
//    "access_token": "ya29.a0...0f",
//    "expires_in": 3599,
//    "scope": "openid https://www.googleapis.com/auth/userinfo.email",
//    "token_type": "Bearer",
//    "id_token": "eyJhb...o5nQ"
//  }

jsonToken := CkJsonObject_Create();
success := CkJsonObject_LoadFile(jsonToken,'qa_data/tokens/google_sample_id_token.json');
if (success = False) then
  begin
    Memo1.Lines.Add('Failed to load the JSON file...');
    Exit;
  end;

//  Get the id_token;
sbIdToken := CkStringBuilder_Create();
success := CkStringBuilder_Append(sbIdToken,CkJsonObject__stringOf(jsonToken,'id_token'));

//  Get the signature in base64url format.
//  The header + payload remains in sbIdToken.
sig_b64Url := CkStringBuilder__getAfterFinal(sbIdToken,'.',True);
headerPlusPayload := CkStringBuilder__getAsString(sbIdToken);

Memo1.Lines.Add(sig_b64Url);
Memo1.Lines.Add(headerPlusPayload);

//  ---------------------------------------------

//  Try validating with each cert's public key.
//  Hopefully one will be the key that verifies.

rsa := CkRsa_Create();
CkRsa_putEncodingMode(rsa,'base64url');

jsonKey := CkJsonObject_Create();
pubKey := CkPublicKey_Create();

numKeys := CkJsonObject_SizeOfArray(json,'keys');
i := 0;
while i < numKeys do
  begin
    CkJsonObject_putI(json,i);

    CkJsonObject_ObjectOf2(json,'keys[i]',jsonKey);

    success := CkPublicKey_LoadFromString(pubKey,CkJsonObject__emit(jsonKey));
    if (success = False) then
      begin
        Memo1.Lines.Add(CkPublicKey__lastErrorText(pubKey));
        Exit;
      end;

    Memo1.Lines.Add(IntToStr(i));
    Memo1.Lines.Add(CkPublicKey__getPem(pubKey,True));

    success := CkRsa_UsePublicKey(rsa,pubKey);

    bVerified := CkRsa_VerifyStringENC(rsa,headerPlusPayload,'sha256',sig_b64Url);
    Memo1.Lines.Add('bVerified = ' + IntToStr(Ord(bVerified)));

    i := i + 1;
  end;

//  The output is:

//  0
//  -----BEGIN RSA PUBLIC KEY-----
//  MIIBCgKCAQEA4RIrO30287Wsq3gqXCMkUYMVAeI3H8LVE6IXR1krdFeGnZLiGUPw
//  cbkeVpXf3lmJdsStOg+jijces2DZCfPyIBiQuLYfxxmAZE6ErJ0QJFg1stwli2Pz
//  9ncYhFoqi8pXr7kEzEJBTzX4thuw56ydbGsshSEznPXoerCJOc7UI2+n0wFCWQ4Y
//  LHbh/PrWt4vdadyUUUW/QpQHXQLdD8q/Qwqdj0O9zlJE7R6Elw2E9EqnHyIGu1hm
//  LxhqrTru1M18SUhONYbVskV/BCEdVKs//X96849HorWQDCAgVMWfGsdMVq55FAdJ
//  680N5UmQDRynIZ4+PeNGN4S9iw2mbMNEBQIDAQAB
//  -----END RSA PUBLIC KEY-----
//  
//  bVerified = True
//  1
//  -----BEGIN RSA PUBLIC KEY-----
//  MIIBCgKCAQEAxT/ngLZNmT5GBdkLtJZjNeTB+8B5yWgrq/e5eMZ1hrZhcmLK+dSn
//  IkpOPV8/OekV67EnQ7I4II2rcNJnHGrGKZziXO3XN2gtUHE+mBJC99oULSbX/QwB
//  Kz7gC/IBPq9EuxTt6Oq6fPkVQ9DbRIgWJSEGBF/KRaNl3kyAlIZfpY7XgHyJTTv8
//  E7yAcYKPR+36gzdl+ps0sDLKzUuAtZNq8llK0u80z6AtAUIYwWdkEhM9upy6keKI
//  TasIxcsO7M6kZPINUSbh6t5VAm8FuqRmxpgg+9c9/GQSGd89InVypoVzWLQ+wOGg
//  5G4H6JqIgtj0TRFt4gK0eoFi2U0d3l8bcwIDAQAB
//  -----END RSA PUBLIC KEY-----
//  
//  bVerified = False

CkHttp_Dispose(http);
CkJsonObject_Dispose(json);
CkJsonObject_Dispose(jsonToken);
CkStringBuilder_Dispose(sbIdToken);
CkRsa_Dispose(rsa);
CkJsonObject_Dispose(jsonKey);
CkPublicKey_Dispose(pubKey);